Pcv valve mounting structure

ABSTRACT

A PCV valve mounting structure which releases freezing of a PCV valve promptly is provided. A PCV valve mounting structure is provided with a resin cover forming an internal space portion between the resin cover and a cylinder head of an internal combustion engine, a valve mounting through hole formed at the resin cover, a PCV valve including a valve case portion inserted through the valve mounting through hole from outside the resin cover, and a metal fixture threadedly engaged, from inside the resin cover, with the valve case portion inserted through the valve mounting through hole, at least part of the metal fixture being exposed to the internal space portion.

TECHNICAL FIELD

The present invention relates to a PCV valve mounting structure including a cover forming an internal space portion between the cover and a cylinder head of an internal combustion engine, a valve mounting through hole formed at the cover and a PCV valve (positive crankcase ventilation valve) including a valve case portion inserted through the through hole from outside the cover.

BACKGROUND ART

In recirculating a blow-by gas to an induction system, a PCV valve is provided to adjust flow amount of the recirculation. The blow-by gas corresponds to gas leaking out from a combustion chamber to an inside of a crankcase in compression/combustion processes of an internal combustion engine, for example. However, because the PCV valve is provided at an outside of a cylinder head and the PCV valve itself is exposed to outside air, moisture included in the blow-by gas attaches to the PCV valve and freezes especially in cold weather, and accordingly the PCV valve may be prevented from operating normally.

Therefore, for example, the PCV valve is mounted on a cover forming an internal space portion between the cover and the cylinder head so that the frozen moisture can be defrosted with heat generated at the internal combustion engine. In a case where the cover is formed by metal having a high coefficient of thermal conductivity, including, for example, aluminum alloy, the heat generated at the internal combustion engine is efficiently transmitted to the PCV valve via the cover made of the metal, and accordingly the frozen moisture can be defrosted promptly. However, in a case where the cover is formed by resin having a lower coefficient of thermal conductivity compared to the metal, efficiency of defrosting the frozen moisture is decreased.

In Patent document 1, a PCV valve mounting structure is described which allows heat generated at an internal combustion engine to be efficiently transmitted to the PCV valve mounted on a resin cover. According to the mounting structure, a portion of the PCV valve, the portion which is exposed to an internal space portion between a cylinder head and the resin cover, is formed by metal whose coefficient of thermal conductivity is high. It is configured in such a manner that efficiency of heat transfer to the PCV valve is enhanced and the frozen moisture is defrosted by heating the metal portion with heat possessed by hot temperature atmosphere of the internal space portion.

DOCUMENT OF KNOWN ART Patent Document

Patent document 1: JP2009-150289A

OVERVIEW OF INVENTION Problem to be Solved by the Invention

However, manufacturing cost of the PCV valve formed with the metal portion exposed to the internal space portion between the cylinder head and the resin cover is higher compared to a PCV valve which does not include such metal portion and whole of which is made of resin, for example. Because the PCV valve is designed depending on a type of an internal combustion engine, also such metal portion needs to be designed for each PCV valve. Accordingly, in providing the PCV valve, inconvenience occurs in aspects of a manufacturing efficiency and costs.

The present invention is made in view of the above-described circumstances, and an object is to provide a PCV valve mounting structure which efficiently transmits heat generated at an internal combustion engine and releases freezing promptly even in a case where the PCV valve is made of resin.

Measures for Solving the Problem

An aspect of a PCV valve mounting structure of the present invention is that the PCV valve mounting structure includes a resin cover forming an internal space portion between the resin cover and a cylinder head of an internal combustion engine, a valve mounting through hole formed at the resin cover, a PCV valve including a valve case portion inserted through the valve mounting through hole from outside the resin cover, and a metal fixture threadedly engaged, from inside the resin cover, with the valve case portion inserted through the valve mounting through hole, at least part of the metal fixture being exposed to the internal space portion.

According to the PCV valve mounting structure including the present configuration, at least part of the metal fixture threadedly engaged with the valve case portion inserted through the through hole is exposed to the internal space portion, and the metal fixture can be heated with heat possessed by hot temperature atmosphere of the internal space portion.

The foregoing metal fixture is applicable to any PCV valve or to any valve case portion, and can be used as a common part. Therefore, the PCV valve itself can be manufactured inexpensively without using metal. In addition, the use of the common metal fixture reduces a manufacturing unit price and makes an inventory control easy, thereby even more increasing efficiency of the PCV valve mounting structure.

An aspect of the PCV valve mounting structure of the present invention is that the metal fixture is integrally provided with a cylindrical screw portion which is insert molded in the resin cover and a heat receiving portion extended from the cylindrical screw portion to protrude into the internal space portion, and the valve case portion is provided with a screw portion threadedly engaging with the cylindrical screw portion.

According to the present configuration, by an operation of threadedly engaging the screw portion, which is provided at the valve case portion, with the cylindrical screw portion, which is insert molded in the resin cover, the PCV valve can be mounted on the resin cover conveniently. In addition, the heat receiving portion protruding into the internal space portion is provided to extend from the cylindrical screw portion, and thus a large area for receiving the heat can be assured. Consequently, the heat possessed by the hot temperature atmosphere of the internal space portion is received at the large area for receiving the heat, and accordingly the cylindrical screw portion can be heated. As a result, according to the PCV valve mounting structure including the present configuration, a freeze protection effect can be even more enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Cross-sectional view of an internal combustion engine provided with a PCV valve

FIG. 2 Cross-sectional view illustrating a PCV valve mounting structure

FIG. 3 Cross-sectional view illustrating a PCV valve mounting structure of a second embodiment

MODE FOR CARRYING OUT INVENTION

Embodiments of the present invention will be described hereunder on the basis of the drawings.

First Embodiment

FIG. 1 and FIG. 2 illustrate an engine (an internal combustion engine) E provided with a PCV valve mounting structure of the present embodiment. As illustrated in FIG. 1, the engine E includes a cylinder head 1, a cylinder block 2, a crankcase 3 and an oil pan 4 which are placed up and down to be arranged one above another, and are connected to one another. A cylinder head cover 5 is provided at an upper portion of the cylinder head 1. The cylinder head cover 5 is made of resin including nylon, for example.

A crankshaft 6 is rotatably supported inside the crankcase 3 and pistons 7 are slidably fitted into plural cylinder bores formed at the cylinder block 2. The pistons 7 and the crankshaft 6 are connected to each other with connecting rods 8.

An air intake valve 9 and an exhaust valve 10 are provided at the cylinder head 1 to be able to open and close. An intake cam shaft 11 and an exhaust cam shaft 12, which are in postures that are parallel to the crankshaft 6, are rotatably supported at upper positions of the air intake valve 9 and the air exhaust valve 10.

An intake manifold 14 is connected to one lateral surface of the cylinder head 1, an exhaust manifold 15 is connected to the other lateral surface of the cylinder head 1. A spark plug 16 igniting air-fuel mixture of a combustion chamber 20 is provided at an upper surface of the cylinder head 1.

An injector 17 supplying fuel to the combustion chamber 20 is provided at an air intake passage provided at the cylinder head 1 and the intake manifold 14 is connected to the air intake passage. A surge tank 18 is provided at an upstream-side relative to the intake manifold 14 and a throttle valve 19 is further provided at an upstream-side relative to the surge tank 18.

Though not shown, an endless chain is wrapped along a crankshaft sprocket provided at a shaft end of the crankshaft 6 and cam sprockets provided at shaft ends of the respective intake cam shaft 11 and exhaust cam shaft 12 so that the intake cam shaft 11 and the exhaust cam shaft 12 are rotated synchronously with rotations of the crankshaft 6. The spark plug 16 and the injector 17 are provided to be controlled by a control apparatus (not shown) including ECU, for example.

Due to the foregoing configuration, when the engine E is operating, the intake cam shaft 11 and the exhaust cam shaft 12 rotate synchronously with the rotations of the crankshaft 6, thereby opening an intake port of the air intake valve 9 due to a compressive force from a cam portion of an outer circumference of the intake cam shaft 11 at a predetermined timing. Similarly, an exhaust port of the exhaust valve 10 is opened due to a compressive force from a cam portion of an outer circumference of the exhaust cam shaft 12 at a predetermined timing.

The control apparatus conducts control so that the injector 17 supplies the fuel to the combustion chamber 20 at the predetermined timing at which the intake valve 9 opens and that the spark plug 16 ignites the air-fuel mixture at a predetermined timing at which the air-fuel mixture of the combustion chamber 20 is compressed.

Inside the cylinder head cover 5, feed oil pipes 21 are arranged above the respective intake cam shaft 11 and exhaust cam shaft 12 to be in postures parallel to the cam shafts 11 and 12. Spray nozzles 21A spraying oil downwardly are provided at the feed oil pipes 21.

Thus, when the engine E is operating, the oil supplied by a hydraulic pump (not shown) to each of the feed oil pipes 21 is sprayed from the spray nozzles 21A to the intake cam shaft 11 and the exhaust cam shaft 12. Though not shown, a discharge port discharging the oil is formed at the cylinder head 1 and an oil passage returning the oil, which is discharged from the discharge port, to the oil pan 4 is formed at the cylinder head 1.

When the engine E is operating, part of mixed gas introduced to the combustion chamber 20 leaks out to a crank chamber 13 from a gap between an outer circumference of the piston 7 and an inner circumference of the corresponding cylinder. The unburnt mixed gas that has leaked in this way is referred to as the blow-by gas. The engine E is provided with a blow-by gas recirculation apparatus recirculating the blow-by gas to the induction system of the engine E and introducing the blow-by gas, together with new mixed gas, to the combustion chamber 20 so that the introduced gas is burnt thereat.

The blow-by gas recirculation apparatus supplies the blow-by gas occurring in the crank chamber 13 to an oil separator 40 provided at an upper portion of the cylinder head cover 5 via a gas extract path 22. The blow-by gas recirculation apparatus transports the blow-by gas, from which oil mist is separated, to a gas space portion S and stores the blow-by gas thereat. The blow-by gas stored at the gas space portion S is sent to a gas return path 23 via a PCV valve 30, and is returned to the induction system (specifically, the surge tank 18) of the engine E to be combusted in the combustion chamber 20 together with the air-fuel mixture.

As illustrated in FIG. 2, the oil separator 40 is fixed at an upper surface of the cylinder head cover 5 while sandwiching a gasket 24, and the oil separator 40 includes inside thereof a cyclone-type separation unit 43 separating and removing the oil mist included in the blow-by gas.

The oil separator 40 is integrally provided with an upper part case portion 41 and a lower part case portion 42, and the gas space portion (an internal space portion) S is formed at an inside of the upper part case portion 41 and the separation unit 43 is provided at an inside of the lower part case portion 42. A dividing wall 44 is formed at an intermediate portion between the upper part case portion 41 and the lower part case portion 42, and a supply space portion T is formed at an outer circumference-side of the separation unit 43 at a lower side relative to the dividing wall 44. As well as the cylinder head cover 5, each of the upper part case portion 41, the lower part case portion 42, the separation unit 43 and the dividing wall 44 is formed by resin material including nylon, for example.

The separation unit 43 includes a cylindrical portion 43A and a funnel-shaped portion 43B integrally formed at a lower side of the cylindrical portion 43A. The separation unit 43 is provided with an opening portion 43H formed at an outer circumference of the cylindrical portion 43A to be in communication with the supply space portion T. The separation unit 43 is provided with a hole portion 43C formed at a lower end of the funnel-shaped portion 43B to be in communication with an inside of the cylinder head cover 5. A through hole 44A is formed at the dividing wall 44 that is at an upper position of the cylindrical portion 43A of the separation unit 43.

Due to the foregoing configuration, in a case where the blow-by gas is supplied to the supply space portion T, the gas including therein the oil mist is introduced from the opening portion 43H to an inside of the cylindrical portion 43A of the separation unit 43 in a tangential direction, and accordingly the gas swirls as the gas is introduced thereto. The oil mist is gathered, collected and separated by an effect of centrifugal force due to the swirling of the gas. The gathered and collected oil mist is sent from an inner surface of the funnel-shaped portion 43B to the hole portion 43C, and then is sent out to the inside of the cylinder head cover 5 via the hole portion 43C. In addition, the blow-by gas from which the oil mist has been removed is led from the through hole 44A of the dividing wall 44 to the gas space portion S.

The PCV valve 30 is mounted on the upper part case portion 41 in a state where the PCV valve 30 is in communication with the gas space portion (the internal space portion) S of the upper part case portion 41. Thus, the upper part case portion 41 serves as a resin cover which forms, together with the cylinder head cover 5, the internal space portion (the gas space portion S) between the upper part case portion 41 and the cylinder head 1 of the engine E, and a valve mounting through hole 41A is formed at the upper part case portion 41 to be transversely arranged.

The PCV valve 30 is provided with a valve main body 31, a valve body 32 accommodated inside the valve main body 31, a support member 33 preventing the valve body 32 from falling off the valve main body 31 and a spring 34 biasing the valve body 32 in a close direction. A hole portion 33A is formed at the support member 33.

The valve main body 31 is integrally provided with a connection cylindrical portion 31A connected to the gas return path 23, a cylindrical main body portion 31B forming an accommodation portion for the valve body 32 and an annular collar portion 31C including, for example, a hexagonal configuration and a different diameter. A male screw portion 31D is formed at an outer circumferential portion of the cylindrical main body portion 31B. The valve main body 31, the valve body 32, the support member 33 and the spring 34 are assumed to be formed by resin material, however, all of them or part of them can be formed by metal material.

The cylindrical main body portion 31B corresponds to a valve case portion which is inserted, from outside the upper part case portion 41, through the valve mounting through hole 41A and the cylindrical main body portion 31B is inserted through the through hole 41A in a state where an insertion depth is restricted by a contact of the annular collar portion 31C and the upper part case portion 41 with each other. A metal fixture 25 threadedly engages, from inside the upper part case portion 41, with the male screw portion 31D of the cylindrical main body portion 31B inserted through the through hole 41A, and the PCV valve 30 is fixed to the upper part case portion 41.

The metal fixture 25 is provided with a cylindrical screw portion 26 formed with a female screw portion 26A which threadedly engages with the male screw portion 31D of the cylindrical main body portion 31B. The metal fixture 25 is insert molded in the upper part case portion 41 in such a manner that the metal fixture 25 is prevented from turning and in such a manner that part of the cylindrical screw portion 26 is exposed to the gas space portion S, and the whole of the metal fixture 25 is made of metal having a high coefficient of thermal conductivity, including aluminum alloy and/or copper alloy, for example.

The part of the cylindrical screw portion 26, the part including a portion which is not embedded in the upper part case portion 41 and including a female screw portion with which the male screw portion 31D does not engage, is exposed to the gas space portion S, and thus the metal fixture 25 is configured to be heated with heat possessed by hot temperature atmosphere including the blow-by gas of the gas space portion S.

The metal fixture 25 is applicable to any PCV valve 30 or to any cylindrical main body portion (the valve case portion) 31B, and can be used as a common part. Therefore, the PCV valve 30 itself can be manufactured inexpensively without using the metal. In addition, the use of the common metal fixture 25 reduces a manufacturing unit price and makes an inventory control easy, thereby even more increasing efficiency of the mounting structure of the PCV valve 30.

The valve main body 31 is fixed to the upper part case portion 41 in a state where the annular collar portion 31C and the cylindrical screw portion 26 sandwich a vicinity around the through hole 41A of the upper part case portion 41. Accordingly, a portion 41B of the upper part case portion 41, the portion 41B being sandwiched by the annular collar portion 31C and the cylindrical screw portion 26, functions as an annular seal material sealing a gap between the cylindrical main body portion 31B and the through hole 41A.

Second Embodiment

FIG. 3 illustrates a second embodiment of the present invention. In the present embodiment, the metal fixture 25 is integrally provided with the cylindrical screw portion 26 that is insert molded in the upper part case portion 41 in a manner that the part of the cylindrical screw portion 26 is exposed to the gas space portion S, and the metal fixture 25 is integrally provided with a heat receiving portion 27 including a plate shape and extended from the cylindrical screw portion 26 to protrude downwardly along a cylinder radial direction into the gas space portion S.

The heat receiving portion 27 is ideally formed in such a configuration that does not easily hinder the flow of the blow-by gas in the gas space portion S. In addition, the heat receiving portion 27 may be provided as a flow passage forming member that forms a flow passage of the blow-by gas in the gas space portion S. The other configuration is similar to the first embodiment.

Other Embodiment

-   1. According to the PCV valve mounting structure of the present     invention, the whole of the metal fixture, which threadedly engages     with the valve case portion from inside the resin cover, can be     exposed to the internal space portion of the resin cover. -   2. According to the PCV valve mounting structure of the present     invention, the valve case portion can be inserted through the valve     mounting through hole, which is formed at the cylinder head cover     made of resin, and at least part of the metal fixture, which is     threadedly engaged with the valve case portion from inside the     cylinder head cover, can be exposed to the internal space portion of     the cylinder head cover.

INDUSTRIAL APPLICABILITY

The PCV valve mounting structure of the present invention is applicable to various internal combustion engines provided with a PCV valve.

EXPLANATION OF REFERENCE NUMERALS

1 cylinder head

25 metal fixture

26 cylindrical screw portion

27 heat receiving portion

30 PCV valve

31B cylindrical main body portion (valve case portion)

31D screw portion

41 upper part case portion (resin cover)

41A valve mounting through hole

E internal combustion engine

S gas space portion (internal space portion) 

1. A PCV valve mounting structure, comprising: a resin cover forming an internal space portion between the resin cover and a cylinder head of an internal combustion engine; a valve mounting through hole formed at the resin cover; a PCV valve including a valve case portion inserted through the valve mounting through hole from outside the resin cover; and a metal fixture threadedly engaged, from inside the resin cover, with the valve case portion inserted through the valve mounting through hole, at least part of the metal fixture being exposed to the internal space portion.
 2. The PCV valve mounting structure according to claim 1, wherein the metal fixture is integrally provided with a cylindrical screw portion which is insert molded in the resin cover and a heat receiving portion extended from the cylindrical screw portion to protrude into the internal space portion, and the valve case portion is provided with a screw portion threadedly engaging with the cylindrical screw portion. 